1. Field of the Invention
The invention concerns a thread brake for a weaving loom, and in particular a thread brake mounted between a weft thread storing means and a weft insertion means, the thread brake including at least one driven, adjustable thread guide which deflects the weft thread in order to brake it.
2. Description of-Related Art
Thread brakes are used in airjet looms to decelerate a weft near the end of its insertion. As a rule they are mounted between a accumulator and a main jet nozzle affixed to the reed batten. In a known weft brake, disclosed in European patent document A 0,527,510, use is made of stationary and movable thread guides. The movable guides are mounted on a support moved by a controlled, electrical drive. Illustratively, the controlled electrical drive is a motor actuated by a control unit at a given time during weft insertion. The angle of deflection of the thread caused by movement of the movable guides determines the extent of braking.
In looms, and especially in airjet looms, weft insertion lasts only a few milliseconds, and consequently such thread brakes must be operated very quickly. The resulting abrupt deceleration of a weft which has been inserted at high speed has the disadvantage of causing a tension spike to arise in the weft, which may result in a rupture, and which also negatively affects the performance of the thread brake itself.
Another thread brake is known from European patent document A 0,356,380. In this thread brake, the thread deflection is achieved by several braking guides, but the performance of the thread brake is still affected by tension spikes, which have the affect of partly reversing the deflection provided by the guides.